[en] This review article describes the identification of the tyrosine kinase BCR/ABL as the hallmark of chronic myeloid leukemias (CML) as well as the development of a specific inhibitor of this tyrosine kinase, the STI571 (Glivec, imatinib mesylate). The authors discuss the results of a phase I and three phase II trials reporting the efficacy of STI571 as treatment for CML patients and propose two simplified algorithms that may help to guide decision-making for the individual patient.